Method of recovering hydrocarbons



Patented Aug. 14, 1945 METHOD OF RECOVERING HYDROCARBON S Frederick E.Frey, Bartlesville, Okla., assignor to Phillips Petroleum Company, acorporation of Delaware No Drawing. Application March 3, 1941, SerialNo. 381,597

, Claims.

This invention relates to a method of recovering hydrocarbons from anunderground reservoir and is especially applicable to the secondaryrecovery of hydrocarbons from oilbearing formations. The method of thepresent invention contemplates the inception and maintenance offlameless combustion within a hydrocarbon-bearing formation for thepurpose of developing temperatures of sufiicient magnitude to effectdistillation and/or cracking of carbonaceous material and to drivethermally volatilized portions of the material from a thermally treatedregion to another location whence it can be readily produced to thesurface of the ground.

The recovery of oil from a subsurface formation may be accomplished byseveral means. a The oil may be initially produced by natural means,such as gas or rock pressure, natural water drive, or solution gaspressure. When these natural forces are insufficient to cause the oil toflow from producing wells at an economical rate, the oil may be pumpedor raised by any desired known method. When pumping methods can nolonger produce oil from a particular formation at an economical rate,additional oil may be recovered by the employment of secondary recoverymethods, for example, by water-flooding or repressuring the partiallydepleted sands. These methods involve the injection of water, gas, air,or a combination of these into the formation through one or more inputwells and the withdrawal of oil" through one or more output or producingwells.

The instant invention, while it relates to secondary recovery in thesense that it is concerned with the production of hydrocarbons from aformation that has beensubstantiaily depleted of natural energy formoving the same through a formation, nevertheless goes much further thanpresent-day methods of increasing the ultimate recovery of hydrocarbonsfrom a given oil-bearing strata. One important aspect of this inventionresides in the fact that it is not dependent on an adequate supply offluid driving medium, as required for the. successful operation of usualsecondary recovery methods, for my invention utilizes any freeoxygen-containing gas, such as air,

to initiate and maintain combustion in a formation for the purposesindicated. Furthermore, the practice of my invention convertshydrocarbons, while they are in the formation, to more desirable formsand thereby reduces and in some cases eliminates the need for treatingor processing the fluid after it reaches the surface of the ground. Aswill be evident from,a perusal of the detailed discussion that appearsfurther along,

my invention affords a number of distinct and highly desirableadvantages over known methods of recovering hydrocarbons.

It is therefore the primary object of this invention to recoverhydrocarbons from subsurface strata.

Another object of this invention is to provide a method of increasingthe ultimate recovery of hydrocarbons from hydrocarbon fluid-bearingformations.

A further object of this invention is to effect distillation and/orcracking-of hydrocarbons in their natural environment.

A still further object is to effect melting and flow of solidified waxydeposits.

These and additional objects and advantages will be readily apparent topersons skilled in the nameless or non-flame oxidation is initiated andmaintained in the formation to thereby heat the oil in the vicinity ofthe input well. Ithas been proposed to generate a flame at the bottom ofthe well and utilize the developed heat to deappreciable damage to theformation. Consider ing an input well as the center of a hot zone,

. it will be apparent that this zone progressively increases in radiusthrough the oxidation of reartively non-volatile carbonaceous materialencountered, the burned out portion of the zone sufficing to preheat airpassing outwardly to regions still unacted upon. Oil in the hot zone.which is thus created is distilled and/or cracked,

depending on the composition of the oil in the formation and thetemperature and pressure within the'zone. Hydrocarbon fluid in theformation,

, together with nitrogen and oxides of carbon resulting from thecombustion, are moved through the formation to one or more output wellsfrom whence they are transmitted to the surface of the ground. 4

The most favorable conditions for the practice of my invention usuallyoccur where a minimum of 250 pounds per square inch total pressure canbe developed without an impracticably large flow of freeoxygen-containing gas, where bottom hole temperatures are suficientlyhigh to initiate oxidation, and where excessive amounts of water do notexist in the formation. These conditions do not always occur, however,and it is therefore essential that the procedure be modified, dependingon existing condition in individual situations. More often, a pressureof 50 pounds per square inch, or even less, will be encountered; and, ina pervious formation or one with pervious zones distributed in a lesspervious formation, the development of pressure by the'introduction ofgas to effect cracking or distillation will not be great. Consequently,means for supplying a proper gas at elevated temperatures to theformation may be necessaryin order to initiate, and sometimes sustain,temperatures high enough for the purposes indicated, and it is a part ofmy invention to provide means for so doing.

Oxidation of heavy hydrocarbons will usually proceed without thedevelopment of flame, but with the development of temperature undermixed phase conditions. Where the oxygen is in the range of 50 to 200pounds per square inch partial pressure or higher, the reactiongenerally requires a temperature of 350 F. or higher to J start, afterwhich the reaction may be successfully maintained within thetemperaturerange of 350 to 600 F. The temperature required to initiatesufficiently rapid oxidation to bring about the necessary temperaturerise is extremely variable, depending on the presence of autocatalyticmaterials. In some instances, a temperature as low as 200 F. suffices toinitiate oxidation to produce the necessary temperature rise.Temperatures at and above this level frequently occur in deep wells.Many shallow formations exist, however, where secondary recovery isdesirable. yet temperature of 120 F., or lower prevail.

Once oxidation is initiated, it will be automatically self-sustainingdue to the temperature development in a particular zone. There areinstances, however, where it may be dimciilt to bring about spontaneousoxidation. Such is the case where high pei'viousness of a formation anda low existing pressure therein necessitate the application of pressurein well bottoms that are below 50 pounds per square inch partialpressure of oxygen. In such instances, and in instances where reactionsets in with difficulty at higher applied pressures, there are certainreaction initiating means which may be applied advantageously. -Forexample, the air or other free oxygen-containing gas that is forced intoa formation through an input well may be admixed with certainsubstances, including water gas, or carbon monoxide. Ammonia or hydrogenmay be used, but because of their cost may best be applied to aid ininitiating the action of a combustion catalyst to be later described.This mixture is passed through a mass of suitable catalyst in the bottomof the well in order to initiate oxidation of these materials by oxygenat ordinary or slightly elevated temperatures. Various catalysts may beemployed,'of which many are known, including those containing thematerials of the iron group, preferably in pyrophoric condition. Theparticular catalyst employed will depend largely upon conditions in aparticular producing horizon. One catalyst which is well suited for thepurposes of this invention is Hopcalite. A free oxygen-containing gaswhich is admixed with carbon monoxide .will, upon coming in contact withHopcalite in the bottom of the well bore, initiate combustion atordinary temperatures. By properly controlling the proportions ofcombustible matter and free oxygen-containing gas, the temperature ofthe gas on passing through the catalyst in a burned condition can beregulated and maintained below flame temperature for such time as itis'essential to develop a sufficiently hot zone in the formation tosustain regular oxidation, whereupon the addition of combustible matterto the free oxygen-containing as may be discontinued and freeoxygen-containing gas alone is injected into the formation. By suitablyregulating the proportions of air and combustible gas and flue gas, ifdesired, both temperature and any desired excess of unconsumed oxygenmay be maintained. There are cases in which it is desirable to continuethe use of the combustible matter after'the initial period in order tomaintain satisfactory operation. The above described combustion is thuscontrollable to avoid destruction of equipment or perviousness of theformation at the foot of the well.

The use of reasonably dry producer gas is recommended where it isimportant that water formation resulting from the practice of myinvention be maintained at a minimum.

While the instant invention comprises the several steps and the relationof one or more of such steps to each of the other enumerated steps, itis to be clearly understood that various changes in the method ofprocedure may be resorted to without departing from the spirit of theinvention, and further that the theories set forth, although believed tobe accurate, are not to be considered as the sole basis of theoperativeness of this invention, but that this method does operatesuccessfully and eflectively whether or not upon the principlesdescribed herein, this invention to be limited only bythe appendedclaims. Minor changes to make a preferred adaptation to any particularsituation may be readily made by one skilled in the art, as trial mayindicate.

I claim:

1. In a method of recovering hydrocarbons from a hydrocarbon oil-bearingformation which is penetratedby an input well and an output well, thesteps comprising transmitting free oxygencontaining gas into theformation through the input well, initiating and maintainin namelessoxidation of carbonaceous material in the for- -mation to heat the oiltherein and effect distillation of relatively low boiling pointcomponents of the oil, and withdrawing distilled components of the oilthrough the output well.

2. In a method of recovering hydrocarbons from a hydrocarbon oil-bearingformation which is penetrated by an input well and an output well, thesteps comprising transmitting free oxygencontaining gas into. theformation through the input well, initiating and maintaining flamelessoxidation of carbonaceous material in the formation to heat the oiltherein and effect cracking of relatively high molecular weighthydrocarbons, and withdrawing cracked components of the oil through theoutput well.

3. In a method of recovering hydrocarbons from a hydrocarbon oil-bearingformation which is penetrated by an input well and an output well, thesteps comprising transmitting free oxygencontaining gas into theformation through the input well, initiating and maintaining flamelessoxidation of carbonaceous material in the formation to effectdistillation of relatively low boiling point components of the oil andcracking of relatively high molecular weight components of the oil, andwithdrawing hydrocarbon fluid through the output well.

4. In a method of recovering hydrocarbons from a hydrocarbon oil-bearingformation which is penetrated by an input well and an output well, thesteps comprising introducing free oxygencontaining gas into the inputwell, transmitting the free oxygen-containing gas through a suitablecatalyst that is disposed in the portion or the in-' put well whichpenetrates the oil-bearing formation to initiate flameless oxidation ofcarbonaceous material in the formation, and withdrawing hydrocarbonfluid through the output well.

5. In a method of recovering hydrocarbons from a hydrocarbon oil-bearingformation which is penetrated by an input well and an output well, thesteps comprising introducing a combustible fluid including free oxygeninto the input well, contacting the combustible fluid with a suitablecatalyst in the portion of the input well that penetrates theoil-bearing formation to initiate flameless oxidation in the formation,and withdrawing hydrocarhonfluid through the outpiit well.

6. In a method of recovering hydrocarbons from a hydrocarbon oil-bearingformation which is penetratedby an input welland an output well, thesteps comprising introducing a combustible fluid including free oxygeninto the input well,

tion in the formation, subsequently discontinuing the transmission ofcombustible fluid through the input well but transmitting sufflcientquantities of steps comprising transmitting a combustible fluidcontacting the combustible fluid with a suitable catalyst of the irongroup in the portion of the input well that penetrates the oil-bearingformation to initiate flameless oxidation in the formation, andwithdrawing hydrocarbon fluid through the output well.

7. In a method of recovering hydrocarbons from a hydrocarbon oil-bearingformation which through the output well.

tinuing the transmission of combustible fluid through the input well buttransmitting suiilcient quantities of free oxy n-containing gastherethrough to sustain flameless oxidation in the formation, andwithdrawing hydrocarbon fluid through the output well.

9. In a method of recovering hydrocarbons from a hydrocarbon bearingformation which is penetrated by an input well and an output well, thesteps comprising transmitting free oxygen containing gas into theformation through the input well, initiating and maintaining flamelessoxidation of carbonaceous material in the formation to heat the oiltherein to a temperature within the range of 200 to 600 F. and eflectdistillation of relatively low boiling point components of the oil, andwithdrawing distilled components of the oil through the output well.

10. In a method of recovering hydrocarbons from a hydrocarbon bearingformation which is' penetrated by an input well and an output well,

the steps comprising transmitting free oxygencontaining gas into theformation through the input well, initiating and maintaining flamelessoxidation of carbonaceous material in the forma-" FREDERICK E. FREY.

